/*
 *  Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You under the Apache License, Version 2.0
 *  (the "License"); you may not use this file except in compliance with
 *  the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */

package java.io;

/**
 * Wraps an existing {@link Reader} and counts the line terminators encountered
 * while reading the data. The line number starts at 0 and is incremented any
 * time {@code '\r'}, {@code '\n'} or {@code "\r\n"} is read. The class has an
 * internal buffer for its data. The size of the buffer defaults to 8 KB.
 */
public class LineNumberReader extends BufferedReader {

	private int lineNumber;

	private int markedLineNumber = -1;

	private boolean lastWasCR;

	private boolean markedLastWasCR;

	/**
	 * Constructs a new LineNumberReader on the Reader {@code in}. The internal
	 * buffer gets the default size (8 KB).
	 *
	 * @param in the Reader that is buffered.
	 */
	public LineNumberReader(Reader in) {
		super(in);
	}

	/**
	 * Constructs a new LineNumberReader on the Reader {@code in}. The size of
	 * the internal buffer is specified by the parameter {@code size}.
	 *
	 * @param in   the Reader that is buffered.
	 * @param size the size of the buffer to allocate.
	 * @throws IllegalArgumentException if {@code size <= 0}.
	 */
	public LineNumberReader(Reader in, int size) {
		super(in, size);
	}

	/**
	 * Returns the current line number for this reader. Numbering starts at 0.
	 *
	 * @return the current line number.
	 */
	public int getLineNumber() {
		synchronized (lock) {
			return lineNumber;
		}
	}

	/**
	 * Sets a mark position in this reader. The parameter {@code readlimit}
	 * indicates how many characters can be read before the mark is invalidated.
	 * Sending {@code reset()} will reposition this reader back to the marked
	 * position, provided that {@code readlimit} has not been surpassed. The
	 * line number associated with this marked position is also stored so that
	 * it can be restored when {@code reset()} is called.
	 *
	 * @param readlimit the number of characters that can be read from this stream
	 *                  before the mark is invalidated.
	 * @throws IOException if an error occurs while setting the mark in this reader.
	 * @see #markSupported()
	 * @see #reset()
	 */
	@Override
	public void mark(int readlimit) throws IOException {
		synchronized (lock) {
			super.mark(readlimit);
			markedLineNumber = lineNumber;
			markedLastWasCR = lastWasCR;
		}
	}

	/**
	 * Reads a single character from the source reader and returns it as an
	 * integer with the two higher-order bytes set to 0. Returns -1 if the end
	 * of the source reader has been reached.
	 * <p>
	 * The line number count is incremented if a line terminator is encountered.
	 * Recognized line terminator sequences are {@code '\r'}, {@code '\n'} and
	 * {@code "\r\n"}. Line terminator sequences are always translated into
	 * {@code '\n'}.
	 *
	 * @return the character read or -1 if the end of the source reader has been
	 * reached.
	 * @throws IOException if the reader is closed or another IOException occurs.
	 */
	@SuppressWarnings("fallthrough")
	@Override
	public int read() throws IOException {
		synchronized (lock) {
			int ch = super.read();
			if (ch == '\n' && lastWasCR) {
				ch = super.read();
			}
			lastWasCR = false;
			switch (ch) {
				case '\r':
					ch = '\n';
					lastWasCR = true;
					// fall through
				case '\n':
					lineNumber++;
			}
			return ch;
		}
	}

	/**
	 * Reads up to {@code count} characters from the source reader and stores
	 * them in the character array {@code buffer} starting at {@code offset}.
	 * Returns the number of characters actually read or -1 if no characters
	 * have been read and the end of this reader has been reached.
	 * <p>
	 * <p>The line number count is incremented if a line terminator is encountered.
	 * Recognized line terminator sequences are {@code '\r'}, {@code '\n'} and
	 * {@code "\r\n"}.
	 *
	 * @throws IOException if this reader is closed or another IOException occurs.
	 */
	@Override
	public int read(char[] buffer, int offset, int count) throws IOException {
		synchronized (lock) {
			int read = super.read(buffer, offset, count);
			if (read == -1) {
				return -1;
			}
			for (int i = 0; i < read; i++) {
				char ch = buffer[offset + i];
				if (ch == '\r') {
					lineNumber++;
					lastWasCR = true;
				} else if (ch == '\n') {
					if (!lastWasCR) {
						lineNumber++;
					}
					lastWasCR = false;
				} else {
					lastWasCR = false;
				}
			}
			return read;
		}
	}

	/**
	 * Returns the next line of text available from this reader. A line is
	 * represented by 0 or more characters followed by {@code '\r'},
	 * {@code '\n'}, {@code "\r\n"} or the end of the stream. The returned
	 * string does not include the newline sequence.
	 *
	 * @return the contents of the line or {@code null} if no characters have
	 * been read before the end of the stream has been reached.
	 * @throws IOException if this reader is closed or another IOException occurs.
	 */
	@Override
	public String readLine() throws IOException {
		synchronized (lock) {
			if (lastWasCR) {
				chompNewline();
				lastWasCR = false;
			}
			String result = super.readLine();
			if (result != null) {
				lineNumber++;
			}
			return result;
		}
	}

	/**
	 * Resets this reader to the last marked location. It also resets the line
	 * count to what is was when this reader was marked. This implementation
	 * resets the source reader.
	 *
	 * @throws IOException if this reader is already closed, no mark has been set or the
	 *                     mark is no longer valid because more than {@code readlimit}
	 *                     bytes have been read since setting the mark.
	 * @see #mark(int)
	 * @see #markSupported()
	 */
	@Override
	public void reset() throws IOException {
		synchronized (lock) {
			super.reset();
			lineNumber = markedLineNumber;
			lastWasCR = markedLastWasCR;
		}
	}

	/**
	 * Sets the line number of this reader to the specified {@code lineNumber}.
	 * Note that this may have side effects on the line number associated with
	 * the last marked position.
	 *
	 * @param lineNumber the new line number value.
	 * @see #mark(int)
	 * @see #reset()
	 */
	public void setLineNumber(int lineNumber) {
		synchronized (lock) {
			this.lineNumber = lineNumber;
		}
	}

	/**
	 * Skips {@code charCount} characters in this reader. Subsequent calls to
	 * {@code read} will not return these characters unless {@code reset}
	 * is used. This implementation skips {@code charCount} number of characters in
	 * the source reader and increments the line number count whenever line
	 * terminator sequences are skipped.
	 *
	 * @return the number of characters actually skipped.
	 * @throws IllegalArgumentException if {@code charCount < 0}.
	 * @throws IOException              if this reader is closed or another IOException occurs.
	 * @see #mark(int)
	 * @see #read()
	 * @see #reset()
	 */
	@Override
	public long skip(long charCount) throws IOException {
		if (charCount < 0) {
			throw new IllegalArgumentException("charCount < 0: " + charCount);
		}
		synchronized (lock) {
			for (int i = 0; i < charCount; i++) {
				if (read() == -1) {
					return i;
				}
			}
			return charCount;
		}
	}
}
